Combustion‐Generated Noise: An Environment‐Related Issue for Future Combustion Systems

Abstract

A first‐order estimation of the prediction of combustion‐generated noise from turbulent premixed flames was explored. The method was based on Lighthill's acoustic analogy and used measurement data from high‐speed imaging of chemiluminescent emissions as input. To determine the noise‐generating source, that is, the overall heat release rate from the measured chemiluminescence signals, numerical simulations were performed for 1 D laminar and 3 D turbulent freely propagating flames by employing detailed transport models and reaction mechanisms, including the full reaction chain of the electronically excited hydroxyl radical (OH*). It was shown for both the 1 D and 3 D cases that the local generation of OH* correlated strongly with the heat released from the chemical reaction, especially in the fuel‐lean range. As the chemiluminescence measurements gathered light only along the viewing direction, the line‐of‐sight summed values of heat release rate and OH* concentration were evaluated from the 3 D simulation, and a quasilinear relationship was identified for these integral values. Hence, a proportionality relation was applied for computation of the integral heat release from measured chemiluminescence intensity. An analytical solution of Lighthill's wave equation served as a transfer function, which took fluctuations in the total heat release rate or light intensity as input to calculate the sound radiation in the far field. This approach was applied to a generic burner operated with premixed methane/air jet flames. Good quantitative agreement was obtained between the sound pressures derived from the chemiluminescence measurements and the microphone data, which highlights the potential of the method for applications to more complex flame configurations.

Large eddy simulation on combustion noise in a non-premixed turbulent free flame: Effect of oxygen enhancement

“…acoustic analogy, acoustic perturbation equations, and stochastic methods. Zhang et al estimated combustion generated noise through combination of a premixed flame experiment OH radical data and an analytical solution of Lighthill analogy [21].…”

Heat Release Rate Markers for Highly Stretched Premixed CH4/Air and CH4/H2/Air Flames

“…It measures the concentration of species produced in an excited electronic state far away from equilibrium. In previous studies, − the chemiluminescence emission from CH* and/or OH* was reported to be a good indicator of HRR. However, the chemiluminescence measurement is based on the total emission along the line of sight and is not spatially resolved, especially in complex flame topologies, such as turbulent flames.…”

Combustion regimes in turbulent non-premixed flames for space propulsion

“…This code uses an implicit scheme to resolve the transient conservation equations for mass, momentum, energy, and species with the Finite Volume Method (FVM) [50,51]. EBI-DNS has been applied and validated in several combustion-related problems in recent years [52,53,54,55,56]. The Cantera [34] routines are used for the computation of detailed chemistry and transport properties, using the mixture-averaged transport model described by Kee et al [57].…”